Classes of sub-phylum Vertebrata:

1) Class-Cyclostomata:

• They are ectoparasites on some fishes.
• They have 6-15 pairs of gill slits for respiration.
• Cyclostomes have a sucking and circular mouth without jaws.
• They have no scales and paired fins.
• Cranium and vertebral column are cartilaginous.
• Circulation is of closed type.
• Cyclostomes are marine but migrate for spawning (laying eggs) to fresh water. After spawning, within a few days, they die. Their larvae, after metamorphosis, return to the ocean.
•  Fertilization is external and they are oviparous.

2) Class-Chondriochthyes:

• They are marine animals with streamlined body.
• They have cartilaginous endoskeleton.
•  Mouth is located ventrally.
• Notochord is persistent throughout life.
• Gill slits are separate and without operculum (gill cover).
• The skin has minute placoid scales.. Their jaws are very powerful.
• Due to the absence of air bladder, hey have to swim constantly to avoid sinking.
• Heart is two-chambered (one auricle and one ventricle).
•  Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g., Trygon).

• They are cold-blooded (poi-kilo-thermous) animals, means they cannot maintain a fixed body temperature.
•  Fertilization is internal and they are viviparous.

3) Class-Osteichthyes:

• Only this class includes both marine and fresh water fishes with bony endoskeleton.
•  Their body is streamlined. Mouth is mostly terminal.
• They have four pairs of gills which are covered by an operculum on each side.
• Skin is covered with cycloid/ctenoid scales.
• Air bladder is present which regulates buoyancy.
• Heart is two-chambered (one auricle and one ventricle).
• They are cold-blooded animals.

• Sexes are separate.
• Fertilization is external and they are oviparous.

4) Class-Amphibia:

• Amphibians can live in aquatic as well as terrestrial habitats.
• Most of them have two pairs of limbs.
• Body is divisible into head and trunk and Tail is present only in some of them.
• The amphibian skin is moist (without scales) and they perform respiration through skin.
•  The eyes have eyelids. A tympanum represents the ear.
• Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca.
• Respiration is by gills, lungs and through skin. The heart is three-chambered (two auricles and one ventricle).
• These are cold-blooded animals.
• Sexes are separate.

• Fertilization is external and they are oviparous.

 

5) Class-Reptilia:

• They show creeping or crawling movements to move.
• They are mostly terrestrial animals and their body is covered by dry scales. Snakes and lizards shed their scales as skin cast
•  Tympanum represents ear.
• Limbs, when present, are two pairs.
•  Heart is usually three-chambered, but four-chambered only in crocodiles.
•  Reptiles are poi-kilo-therms.
• Sexes are separate.
• Fertilisation is internal and they are oviparous.

6) Class-Aves:

• Aves means birds have feathers and most of them can fly except flightless birds(Ostrich).
• They possess beak in-spite of mouth to feed.
• The forelimbs are modified into wings. The hind limbs are modified for walking, swimming etc.
• Skin is dry without glands except the oil gland at the base of the tail.
• Endoskeleton is made up of bones.
• Heart is completely four-chambered.
• They are warm-blooded (homo-iothermous) animals, means they are able to maintain a constant body temperature.
•  Respiration is by lungs. Air.
• Sexes are separate.

• Fertilisation is internal and they are oviparous.

 

7) Class-Mammalia:

• They are found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and dark caves.
• The most unique mammalian characteristic is the presence of milk producing glands (mammary glands) by which the young ones are nourished.
• They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying.
• The skin of mammals is unique in possessing hair.
• External ears or pinnae are present.
• Different types of teeth are present in the jaw.
• Heart is fourchambered.
• They are homoiothermous.
• Respiration is by lungs.
•  Sexes are separate.
• Fertilization is internal and they are viviparous.